This application is based on and incorporates herein by reference Japanese Patent Applications No. 2001-179118 filed on Jun. 13, 2001, No. 2001-199392 filed on Jun. 29, 2001, No. 2001-204023 filed on Jul. 4, 2001, and No. 2002-62394 filed on Mar. 7, 2002.
The present invention relates to a method for manufacturing a printed wiring board, in which an electric device is embedded in an insulating base member, and to the printed wiring board manufactured by the method.
Conventionally, a printed wiring board, in which an electric device is embedded in an insulating base member for achieving high density packaging of the electric devices, is known.
For example, there is an art disclosed in JP-A-11-312868. In the art, a plurality of first resin films that make up an insulating base member are formed. The first resin films include thermosetting resin in B stage. A plurality of vias are formed in each first resin film. A plurality of conductive layers are formed on a surface of each first resin film. Then, a second resin film is formed. The second resin film has a glass transition temperature higher than the curing temperature of the first resin films. An electric device sealed with resin is mounted on the second resin film. The second resin film is stacked with and pressed with the first resin films to form an integrated body of the first and second resin films. Subsequently, the thermosetting resin included in the first films is cured by heating the integrated body to manufacture a printed wiring board, in which the conductive layers are electrically interconnected by the vias, the electric device is electrically connected to the conductive layers, and the electric device is embedded in the insulating base member.
However, in the art of the publication, there is a difficulty in the alignment of the electric device with the insulating base member, which is formed when the thermosetting resin included in the first films is cured, in the printed wiring board because the second resin film, on which the electric device is mounted, is clamped between and stacked with the first resin films. Therefore, a relatively great deviation in the alignment can cause a defect in electrical contact between the electric device and the vias.
There is another art disclosed in JP-A-4-356998. In the art, a recess is formed by counter boring in an insulating base member of a double-sided board, which makes up an inner layer board of a multilayered board. Then, an electric device is placed in the recess and soldered. Afterward, the double-sided board, on which electric device is soldered, is multilayered by stacking and pressing pre-pregs on both surface of the double-sided board to manufacture a printed wiring board with the embedded electric device.
However, in the art of JP-A-4-356998, the manufacturing process is complicated and the number of manufacturing steps increases because the pre-pregs are separately piled on the double-sided board.
The present invention has been made in view of the above aspects with an object to provide a method for manufacturing a printed wiring board having an embedded electric device, with which the electric device is readily aligned with an insulating base member of the printed wiring board and with which the manufacturing process can be simplified, and to provide the printed wiring board manufactured by the method.
The method includes steps of forming an opening in a first resin film made of thermoplastic resin, stacking the first resin film and a plurality of second resin films, which are made of the thermoplastic resin and on which a plurality of conductive layers are formed, inserting an electric device, which has substantially the same size as the opening, in the opening, and bonding the stacked first and second resin films together by pressing and heating. When the stacked first and second resin films are pressed and heated, a plurality of electrodes of the electric device are electrically connected to the conductive layers while the first and second resin films are plastically deformed to seal the electric device.
Alternatively, the method includes steps of forming a recess or an opening in a sheet member made of thermoplastic resin, stacking resin films, which are made of thermoplastic resin and on which a plurality of conductive layers are formed, placing the sheet member on an outer surface of or in a stacked body, which is formed in the step of stacking, of the resin films, inserting an electric device in the recess or the opening, and bonding the resin films and the sheet member by pressing and heating. When the resin films and the sheet member are pressed and heated, a plurality of electrodes of the electric device are electrically connected to the conductive layers while the thermoplastic resin is plastically deformed to seal the electric device.